1. Field of Invention
This invention relates generally to improvements in designs of baffles employed in automotive engine applications. More particularly, the invention relates to improvements in the manufacture of automotive engine cover applications, including valve covers, which are designed to reduce noise and vibration.
2. Description of the prior Art
Baffles for automotive engine valve covers have been traditionally formed of a single layer of thin stamped metal, such as steel. Such baffles are used generally not only to aid in the removal of oil mist entrained in crankcase gases, but are also designed to optimize crankcase air flow through the valve cover.
To the extent that the thin metal baffles have often been a source of noise, particularly as induced by engine vibrations, one recurrent theme with respect to such baffles has thus been the need for reducing such noise and for dampening vibrations. Several means of resolving the noise and vibration issues have been attempted; most typically have involved the use of foam coatings, others have made use of liquid gaskets (RTV). While many of the attempted efforts have been laudable, their benefits have often been costly and less than desirable in most cases.
The present inventors have felt that material improvements involving the actual physical structures of the baffles employed in automotive engine valve covers would undoubtedly produce longer lasting noise and vibration control benefits.
The present invention provides a constrained layer damped steel baffle for an engine cam cover. The baffle is designed to aid in the separation of oil mist entrained in a stream of crankcase air vented through the cam cover, and to direct the air to a positive crankcase ventilation (PCV) valve atop the cover. The baffle is also designed to block airborne noises generated within or otherwise resonating from within the cover. The baffle seals off a channel through which the air flows; oil droplets are enabled to condense on the channel walls or baffle and drain to an engine oil sump. The interface between the baffle and the cam cover may be sealed with a foam gasket or a liquid applied room temperature vulcanized (RTV) rubber based sealant.
As disclosed, the baffle is physically constructed of two metal layers joined together by a thin layer of viscoelastic adhesive. The adhesive converts vibrational energy into heat, and thus the baffle will be dampened from resonant engine vibrations. As such, peak amplitudes of vibration will be significantly lower than for single layer plain steel baffles; and lower amplitudes of vibration equate to lower sound radiation levels. As disclosed, the viscoelastic layer will have a thickness in a range of up to 0.15 mm. The individual steel layers will have thickness ranges of 0.2 to 0.6 m.